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Should drainage basins be managed or natural? Discuss with use of examples from both LEDCs and MEDCs.

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Introduction

Should Drainage Basins be managed or natural? Discuss with use of examples from both LEDCs and MEDCs. Drainage basins are areas in which water drains from higher land to lower land and eventually meets the sea or a lake. Water that flows on top of land along a certain path is said to be in a channel. The argument in this essay is whether drainage basins and river channels should be managed or left to flow naturally. If people try to control or alter the natural flow of water in a drainage basin in some way it is said to be managed. If a drainage basin is left alone and has not been changed or altered in any way it is said to be natural. People change drainage basins and river channels for many reasons; one of the earliest examples of drainage basin management was the irrigation of crops around the Nile in ancient Egypt. People change the landscape around them to make it easier for them to live in a particular area, this was thought of as a good thing by many when the UK was newly developing. ...read more.

Middle

The US army corps, in charge of flood prevention, had constructed lev�es, some of which were over 15 m high. They cut through meanders shortening the river (for over 1094 miles it flows in artificial channels). Large floodwater over-spills were built to take the excess water in times of flood. The Mississippi's three major tributaries (The Missuori, Ohio and Tennessee) had been controlled by dams. Despite all of all of these flood defences, the Mississippi still flooded. There were two main views on the cause of the flood; conservationists thought that the flood defences had exaggerated the flood and those in favour of the flood defences blamed it on exceptionally high rainfall. I think that the flood was caused by prolonged rainfall and that the flood defences turned what would have been a long minor flood into an extreme flash flood. This happened because the dams stored up the excess water until they were forced to release some, because of this the river level rose and caused some lev�es to be breached. Another fault of the US army corps engineers was the straightening of the river, this allowed the water to flow faster and gather more energy making it more likely to burst through the lev�es. ...read more.

Conclusion

When lev�es are built to "protect" crops and farmland no silt is deposited (unless lev�es are unsuccessful) and more artificial fertilisers need to be added to enrich the soil. Another reason why drainage basin management is not a good idea is the huge capital needed (although some can be retrieved through Hydroelectricity). Dams and alterations to rivers cost millions and can take years to construct. Even when they are in operation, they need constant maintenance and major repairs to dams are very difficult. It is very difficult to predict what a river is going to do and how it is going to react to changes made to it. This means that there is always a possibility that alterations made in an attempt to manage a drainage basin will not work at all or even make the problem worse. The management of drainage basins also has detrimental effects on the environment, Dams flood valleys and dry up wetland downstream e.g. in 1780 there were 41.9 million acres of wetland around the Mississippi compared to 18.1 million acres today Although I can see the need to protect settlements from flooding and the advantages of hydroelectric power, for me it is the true unpredictability and complex nature of drainage basins that makes management of them a less preferred option. ...read more.

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